Metacaligus uruguayensis Thomsen, 1949

Venmathi Maran, B. A., Ohtsuka, Susumu & Shang, Xu, 2012, Records of Adult Caligiform Copepods (Crustacea: Copepoda: Siphonostomatoida) in Marine Plankton from East Asia, Including Descriptions of Two New Species of Caligus (Caligidae), Species Diversity 17 (2), pp. 201-219 : 212-213

Metacaligus uruguayensis Thomsen, 1949 ( Fig. 9B )

Caligus (Metacaligus) uruguayensis Thomsen, 1949: 3 ; Pillai 1963: 68; Ho and Bashirullah 1977: 708; Boxshall and Montú 1997: 1-225.

Caligus longicervicis Gnanamuthu 1950: 115 ; Kirtisinghe 1964: 65.

Material examined. One adult ♀ (KMNH IvR

500,508), Osaka Port, Osaka Prefecture, Japan (St. 4), 5

October 2008 ( Table 1).

Description. Female. Body ( Fig. 9B ) 4.09 mm long excluding caudal setae. Cephalothoracic shield subcircular, slightly longer than wide, 1.59× 1.48 mm. Fourth pediger wider than long, 0.37× 0.44 mm. Genital complex subquadrate, longer than wide, 1.23× 1.01 mm. Abdomen longer than wide, 0.67× 0.36 mm, unsegmented. Caudal ramus longer than wide, 0.14× 0.07 mm, armed with 3 short subterminal and 3 long terminal setae.

Remarks. Five species of Metacaligus are currently known worldwide: M. rufus (Wilson 1908) from North America; M. uruguayensis Thomsen, 1949 from Uruguay ( Thomsen 1949), India ( Pillai 1963), Sri Lanka ( Kirtisinghe 1964), Venezuela ( Ho and Bashirullah 1977), and Brazil ( Boxshall and Montú 1997); M. unguidentatus Rangnekar and Murti, 1950 from India ( Pillai 1985); M. hilsae ( Shen, 1957) from China ( Shen 1957); and M. latus Ho and Lin, 2002 from Taiwan ( Ho and Lin 2002). This is the first record of this species in Japanese waters.

Distribution. Metacaligus has been regarded as hostspecific to the genus Trichiurus Linnaeus, 1758 . It has so far been found on T. haumela (Forsskål, 1775) in India ( Gnanamuthu 1950), T. lepturus Linnaeus, 1758 in Uruguay ( Thomsen 1949) and Venezuela ( Ho and Bashirullah 1977), and T. savala Cuvier, 1829 in India ( Pillai 1963) and Sri Lanka ( Kirtisinghe 1964). However, it was also recorded from Lobotes surinamensis (Bloch, 1790) in Taiwan ( Ho and Lin 2002).

Figures

Fig. 9. Two other caligid genera from plankton samples. A, Lepeophtheirus semicossyphi Yamaguti, 1939, female (KMNH IvR 500,507), habitus, dorsal view; B, Metacaligus uruguayensis Thomsen, 1949, female (KMNH IvR 500,508), habitus, dorsal view.Scale bars: 1mm (A–B).